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S15 6 speed transmission on an L28


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#1 d3c0y

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Posted 13 February 2012 - 01:29 PM

Hey Guys,

I know someone asked a while back about an S15 six speed in a zed, so here is a link to one if interested.

http://translate.goo...ofs30/ztop1.htm



#2 1600dave

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Posted 13 February 2012 - 05:13 PM

Not a zed, but here's a link to putting one behind an L18 in a 1600. It actually fits in quite nicely, better than using an SR20 5 speed with an L-series bellhousing (the S15 ends up shorter, so its much close in length to the original L-series box).

http://www.ozdat.com...php?f=8&t=25102

I can hopefully post a report on how it drives in another few weeks, just waiting on my LSD centre to be swapped into a 4.44 diff and I can put it all back together.  ;D



#3 juz0

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Posted 13 February 2012 - 06:09 PM

cool. thanks for the link
didn't show what they did with the bell housing though.
i'm interested in doing this one day for shits and giggles since i have a spare
I read on hybrid z that a company is designing adaptor plates for a 350z 6 speed to go on an L28
i have a thing for 6 speeds.....  ::)

#4 d3c0y

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Posted 13 February 2012 - 06:19 PM

Not a zed, but here's a link to putting one behind an L18 in a 1600. It actually fits in quite nicely, better than using an SR20 5 speed with an L-series bellhousing (the S15 ends up shorter, so its much close in length to the original L-series box).


From the threads on here i thought SR20 5 speeds were shorter than Zed boxes and Zed boxes are longer than the 4cyl ones i think?

I read on hybrid z that a company is designing adaptor plates for a 350z 6 speed to go on an L28
i have a thing for 6 speeds.....  ::)


I think they are similar boxes arent they?

#5 1600dave

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Posted 13 February 2012 - 07:33 PM

Here's how I did mine

Cut a few inches off the S15 bellhousing, and made a jig to hold it square and in line with the crank centreline.

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Cut a few inches off the front of an L-series bellhousing, and bolted that up to the rear of a spare block. Then bolted the S15 section of the bellhousing (mounted on its jig) into the three rear main bearings of the block.

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Then welded the two bellhousing section together (this looks to be how the one in your link has been done as well)

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My finished box.

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I am using a standard L-series clutch / clutch throwout lever / throwout bearing / throwout bearing carrier / slave cylinder. Had to make a custom gearbox x-member (although, amazingly, it bolted up using the standard datsun 1600 bits  :o) I made a custom x-member anyway, as the exhaust fouled on the stock x-member.

Tailshaft needed shortening a little and the front yoke is different between the 6 speed and the 5 speeds.

Shifter ended up being maybe two inches further back than a  240K box.

doesn't have provision for a speedo cable (I use GPS / Racechrono for the rare occaision I drive it on the street anyway)


You're right - the 6 speed box is slightly longer than an SR20 / CA18 box, which is in turn longer than a zed box. However, to use a 6 speed on an L-series, you need to trim around 2 inches out of the length of the bellhousing so it ends up being in between a zed box and an SR20 box for length. Here's all three - from left to right - S15 6 speed (with the bellhousing already shortened) / CA18 / 240K / 1600 4 speed.

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From poking my head under my brother's 350Z and waving the tape measure around, the 6 speed out of one of them looks much "fatter" and may be more difficult to fit in the transmission tunnel (although I was looking at it for a 1600 tunnel, not the tunnel out of one of those oversize, overweight zeds  ;) ). They also seem to be much more expensive and not as readily available as the S15 box.

I'm doing it for the much closer ratios - 3.6 / 2.2 / 1.5 / 1.2 / 1.0 / .76, my idea is to use 2nd thru to 6th as 1st thru 5th (using a 4.44 diff) and only use 1st for loading on the trailer

#6 RB30X

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Posted 13 February 2012 - 09:53 PM

Having a six speed lets you run short diff gears and still be able to cruise at high speeds.

#7 dat2kman

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Posted 13 February 2012 - 11:06 PM

Dunno, but,,, if ypu could obtain a fifth gear from a s13 or s14 sylvia, ratio is 0.832, and, if it could be replaced into the sixth gear set in the s15 box, this would give you less engine rpm drop on fifth to sixth upchange, important in a circuit situatipn!

Guys who have fitted rb20det or vl commdore box 71C that have fourth at 1.0 and fifth at 0.75, with lesser powered cars, ie atmo, find it is like hitting a brick eall.

With sixth in the s15 at the "back" just like in s13/14, and being hopefully all the same, it could swap in.

Other definate benefit of s15, forgatting first at horrible 3.6, mated to a 4.4 or 4.8 diff, puts ypur start line first gear as dogleg to left and down ( second gear) and the rest are in H pattern, as you wont be going back into your"first" (second stock) gear once started in a circuit situation.

Yes i realise, it wont give you a low rpm cruose gear, but for tack work the swap to s15 sixth will be beneficial

#8 juz0

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Posted 14 February 2012 - 08:27 AM

anybody want to make a jig for mating the l28 to an s15 box  ;D
i dont have the tooling to do it.......

only problem i guess with the s15 box is the 3/4th gear circlip under lots of load.
they are very hit and miss on how much abuse they can take
lots of guys i've talked to put it down to how you drive it more than anything

#9 1600dave

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Posted 14 February 2012 - 08:35 AM

Same gearbox but out of a Toyota IS200 uses 0.869 6th gear.

Nismo makes a 0.862 6th gear (plus a 2.9 1st if you're really keen). Not overly expensive @ around $400-ish for the 6th gear setup.

With more money, you could build up quite a nice box for the track.  Or just buy a brand new Nismo 6 speed for $4000 or so.  I'm just looking to get a close ratio box on the cheap, has only cost me around $1000 all up including buying the gearbox and getting the tailshaft made. I'll be using it as you suggest, 4.44 diff, 1st will only be for getting it up my driveway, onto the trailer, etc.

#10 1600dave

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Posted 14 February 2012 - 08:37 AM

anybody want to make a jig for mating the l28 to an s15 box  ;D


Like this ??

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I might knock up another one or two bellhousings at some point down the track (late this year maybe), after my setup is complete and fully track-tested.

#11 juz0

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Posted 14 February 2012 - 12:02 PM

1600dave if you make any more let me know and i'll grab one off you

#12 d3c0y

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Posted 14 February 2012 - 10:42 PM

How far off is the S15 bell housing from an L-Series?

#13 1600dave

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Posted 15 February 2012 - 08:49 AM

In terms of bolting an L-series bellhousing onto an S15 6 speed ? Miles out - the two boxes are made by completely different manufacturers, S15 is a "3-part" gearbox (bellhousing / centre section / rear extension) vs the L-series which is just a bellhousing section and a rear extension with a sandwich plate in between them.

The L-series bellhousing swap onto the earlier SR20 5 speed gearbox works because they are basically the same box.



#14 dat2kman

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Posted 15 February 2012 - 10:15 AM

DW, just a funny thougjt, what if, just say, the old front section of a early 240 3 piece bell type box, just happened to bolt onto the S15, might need a few holes massaging!!..that way, an early 2000 Dato front bell could also be bolted onto a S15.

Is the "middle" of the S 15 the same as Mazda mx5 or series 4 on RX7, and Lexus IS200??
I think it is Aissin ?? who makes these?

#15 juz0

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Posted 15 February 2012 - 11:39 AM

the is200 is the same box but the output shaft has a different spline count


#16 juz0

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Posted 30 May 2012 - 08:02 PM

Hey guys
Just got a little more information to add to this.
found some info on setting up a speed sensor.
earlier models of s15 6 speeds have a removable plug at the rear of the box under the shifter.
A modified speedo cog from an s14 5 speed can be fitted and a speed sensor from an s14 can be used as well.
from what i've read the speedo cog just needs to be machined to fit the shaft and some circlips and a detent ball is all thats needed to hold it in place.
the shaft has the circlip grooves already from factory.
I cannot confirm the circlip grooves in the shaft but i can confirm the plug in the gearbox.
I've got 2 6 speeds. the '99 model s15 box has the removable plug but the '01 box doesn't.

i was reading about it on these 2 pages
http://www.the510rea...hp?f=32&t=14753
http://www.the510rea...=5992&start=255

here is a pic with where the plug is located
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Justin

#17 1600dave

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Posted 30 May 2012 - 10:29 PM

I was given these measurements - from what I can see, the worm gear on the output shaft needs 1/16" taken out of the bore to fit the larger diameter output shaft on the 6 speed. I have also been told that only the 6 speed boxes with the "plug" on the rear extension housing have the output shaft machined ready for the worm gear. The later "blanked off" rear extension housing type boxes have a plain (non-machined for worm gear) output shaft.

This is hearsay (but from a reliable source), I didn't take mine apart to confirm whether it had the grooves and ball bearing "hole" or not (mine is the later "blanked-off" rear extension type box. The last pic is of the "plug" type rear extension housing (ie the "good" type of box to use if you want a speedo drive).

Mine is all in the car now, should be out of the shed in a week or two for initial testing, then down to Phillip Island in early August for a "real" workout.

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